Continuing improvements in circuit design and semiconductor processing methodologies have made it possible to integrate in a monolithic miniaturized packaging scheme substantially all of the circuit elements of which an RF signal processor may be configured. One such packaging technology involves the use of modular plug-in devices, such as the improved TO-style cans described in copending U.S. patent application Ser. No. 888,934, entitled "Plug-in Package for High Speed Microwave Integrated Circuits", filed July 24, 1986 and assigned to the assignee of the present application. Through an improved mounting configuration and conductor/dielectric (pin/glass) interface, an impedance match through the signal transmission path between the MMIC and the external world is maintained, so that the plug-in package may be readily interfaced with miniaturized microwave transmission line structures. One transmission line structure that is particularly useful for interconnecting and providing an integrated support structure for components that operate at such high frequencies (e.g. on the order of 20 GHz or more) is a miniaturized periodic transmission line architecture known as `waffleline`, described in detail in U.S. Pat. No. 4.695,810, issued Sept. 22, 1987 and assigned to the assignee of the present application.
Now, although these packaging and interconnect schemes provide a practical hardware approach to system miniaturization and integration, the extremely close proximity of the pins (e.g. on the order of 100 mils) of the plug-in packages has made access to individual signal conductors for purposes of testing the devices extraordinarily difficult. Moreover, in order to successfully test a device not only is it necessary to isolate each respective pin, but the requisite impedance match through the test path must be maintained.